Where is the usercontroller code

[huiwq1990]

• Title: feature title
• Description: your thoughts about this feature
  I think it's better maintain by yurt-app-manager.

[rambohe-ch]

@huiwq1990 I think it's confused for end user there are a lot of controller components in OpenYurt, like yurt-controller-manager, yurt-app-manager, yurt-edgex-manager, raven-controller-manager etc. on the other hand, it's very hard to manage or maintain so many controllers.
I think maybe we should collect all controllers and place them into yurt-controller-manager in the future like kube-controller-manager component in K8s. of course, we need to discuss this case in more bigger scope like community meeting.
so i'd like to suggest that placing userController in Yurt-Controller-Manager will be better decision.